Aggregate all customer names into a single list from the customers table.
CREATE TABLE customers (customer_id varchar, firstname varchar); INSERT INTO customers (customer_id, firstname) VALUES ('C001', 'John'),('C002', 'Jane'),('C003', 'Doe');
```sql
SELECT GROUP_CONCAT(firstname) AS customer_names FROM customers;
```
```sql
SELECT STRING_AGG(firstname, ', ') AS customer_names FROM customers;
```